Cellular events resulting from hormonal, pharmacologic and environmental stimuli and which are mediated via the action of cyclic AMP-dependent protein kinase (ATP: protein phosphotransferase, E.C. 2.7.1.37) were studied in various tissues. Photoaffinity labeling of protein kinase regulatory subunits was employed in determining stimulus-dependent redistribution of isoenzymes in subcellular fractions. Intracellular localization of protein kinase regulatory subunits was established using EM immunogold labeling on thin sections and quantitated by morphometric procedures. Distribution of the regulatory subunits of type II protein kinase in stimulated parotid and other secretory cell types was determined by the EM immunogold method using monoclonal antibodies to type II regulatory subunit. We have previously shown that protein kinase regulatory subunits are components of saliva. Their presence was directly demonstrated in secretory granules of parotid acinar cells, in cells of the seminal vesicles, exocrine and endocrine pancreatic cells, and in pituitary and intestinal endocrine cells. These findings were verified by the presence of 8-azido-cyclic AMP-labeled proteins (R subunits or their proteolysis products) in the secretory fluids of salivary glands, seminal vesicles and the pancreas. It appears, therefore, that protein kinase regulatory subunits are secretory proteins in addition to serving their intracellular roles. Immunogold localization was employed to determine the effects of stimulation with FSH on regulatory subunit distribution in ovarian granulosa cells. Photoaffinity labeling was used to determine the distribution of isoenzymes in rat heart muscle from animals flown in the NASA Space Lab-3 and in monkey and rat cardiac tissues from simulated reduced gravity or increased gravity experiments. Gingival tissues were used to test the effects of wound healing on protein kinase activity and distribution.